This invention relates to an improved process for separating feldspar from siliceous sand, i.e. quartz sand, by means of froth flotation. More particularly, this invention relates to a process for effectively separating feldspar from siliceous sand by using a specific flotation agent under an acidic condition provided by hydrochloric acid.
Flotation, especially froth flotation, is well-known among the general mineral recovery processes such as magnetic separation processes in which useful ore constituents are separated by utilizing a difference in the magnetic forces of the ore constituents and gravity concentration processes in which useful ore constituents are separated by utilizing a difference in the specific gravitites of the ore constituents.
In a conventional froth flotation process, feldspar has been separated from ores usually by pulverizing the ores into a proper particle range, classifying the particles according to size, subjecting them to an activation treatment with hydrofluoric acid, admixing them in water together with a collector (for example, an aliphatic amine) and a foaming agent (for example, pine oil), introducing air thereinto to cause bubbling, and recovering the feldspar in the froth or foam thus generated, while leaving other ore constituents, such as quarz, as tailings.
However, the hydrofluoric acid used as the activator in this process reacts violently with other substances due to its high reactivity. Further, the hydrofluoric acid is a highly poisonous reagent and therefore, must be handled with the greatest possible care. In addition, hydrofluoric acid has the disadvantage of attacking and dissolving the surface of the quartz with a reduction in the yield of the product. Because of these disadvantages and drawbacks, the use of this activator is not desirable in carrying out this process on a commercial scale.
With a view to overcoming these drawbacks caused by the use of hydrofluoric acid in the conventional separation processes, I already proposed a process for effectively separating feldspar from siliceous sand wherein froth flotation of ores is effected by using a combination of a higher aliphatic amine and a petroleum sulfonate as the flotation reagent in the presence of sulfuric acid (U.S Pat. No. 3,844,939). However, this sulfuric acid flotation process tends to entrain fine particles of siliceous sand in feldspar particles during the froth flotation treatment. Consequently, two treatments, i.e. the primary and secondary froth flotation treatments, are required to recover feldspar with good quality. In this process, some difficulty exists in adjustment of the concentration of sulfuric acid, the adjustment being necessary to prevent the precipitation of an insoluble substance formed by the reaction of sulfuric acid with the amine. Thus, this process still has shortcomings in practical use and there is a great demand for developing a practical and satisfactory process for effectively separating feldspar from siliceous sand by means of froth flotation.